There are also products available from auto restoration supply companies such as Eastwood.
You can restore wheels yourself with great success. Lots of epoxys on the market to fill the cracks with ,but I would recomend using an automotive quality paint to finish. Over the counter rattle can paints do not hold up as well due to the lack of hardner in them.
There are companys that restore steering wheels as well but last time I checked they were costly. For a source for these places check the ads in Hemming's or other classic car mags.
Karl.